Program 1 The standard cosmological model 2 The

Program 1. The standard cosmological model 2. The observed universe 3. Inflation. Neutrinos in cosmology

The flatness problem (I) Rewrite Friedmann eq. as Spatial flatness

The flatness problem (II) unstable How our universe can be so flat today ?

The horizon problem t_0 t_LS Acausal volumes in our present Hubble volume How can be the CMB so uniform with no previous contact ?

Inflation Period with Simplest example: (cosm. ct. ) Solves flatness problem

Inflation horizon physical scale expansion scale Solves homogeneity problem

Inflation models Inflaton field evolving slowly in potential INFLATION Inflaton fluctuations produce perturbations Adiabatic (equal entropy per particle) Almost scale invariant (equal amplitude for all wavelengths)

cosmology and neutrinos

Impact of cosmology on neutrino properties - Complementary to properties obtained in solar/atmospheric/laboratory exps - is a “Cicerone” of the universe; it plays or may play a role in almost all epochs of the universe Big Bang Nucleosynthesis Cosmic Microwave Background Large Scale Structure …

in the early universe Cicerone

Expanding universe Luminosity distances Rate of expansion

Neutrinos in thermal equilibrium Weak interactions Interaction rate Equilibrium when Number density Equilibrium distribution (No chemical potential)

Neutrino decoupling rates after decoupling density dilutes and keep form because both (provided m<<T) (Exactly the reason why we observe photon black body today)

Neutrino “temperature” From entropy cons. relic neutrino background (CNB) Properties of CNB can be obtained from CMB

Big Bang Nucleosynthesis (BBN) Production of primordial nuclei - Helium mass-fraction - Deuterium and other light elements number-fraction … From PDG 2006

BBN Light element production depends on number neutrinos Does not depend on mass provided (what it is important is the expansion rate) Parameterize deviations from In fact, (neutrino decoupling near e+e- annih. ) N_eff takes into account other possible light fermions or bosons, even if not fully in thermal equilibrium with the rest

BBN limits on neutrinos Attitude has changed since baryon density is deduced from CMB observations Tension between D and 4 He, with 4 He less in agreement with CMB Probably 4 He systematics Limits on Neff are “author dependent” Evidence of cosmol. nus BBN may also probe non-standard interactions of neutrinos Review: Sarkar, hep-ph/9602260

BBN NOT in crisis

BBN and asymmetries Possibility not as constrained as for charged particles Introduce general distribution with chemical potentials 1.

BBN and asymmetries 2. In principle, good bounds for nu_e and not as good for nu_mu and nu_tau BUT, take into account mixing/oscillations (Use density matrices to describe evolution) Tendency to flavor equilibrium

Flavor evolution in BBN epoch Preferred solution Dolgov et al hep-ph/0201287 Updated bound Serpico & Raffelt astro-ph/0506162 Consequence: standard expectations on neutrino density OK

in the late universe Cicerone

Standard Cosmological Model

Cosmological Observations CMB, LSS, SNIa Ly-alpha, lensing, …

Standard Cosmological Model

DM neutrinos The bulk of the cosmological dark matter has to be cold. Neutrinos have to be subdominant. OK with masses we have measured (excluding highly degenerate masses) cf. Structure formation lead by NR matter, impact of nus on structure formation? 1. 2. move at v=c

Structure formation Graph from Raffelt

Small scales affected Neutrino free-streaming suppreses growth of (small scale) structures Evolution equation at small scales (& other assumptions) (Notice Solution ) Small f_nu, MD univ. Expect change at scales smaller than horizon when nu become NR

Power spectrum Lesgourgues, Pastor hep-astro/0603494

Power spectrum From Strumia & Vissani hep-ph/0606054

Neutrino mass and Cosmic Microwave Background Mass effect in CMB Massive nu goes from R to NR : *** R-M equality Change in expansion rate history Time variation of potentials in RD vs MD No big effects (not as large as LLS) but CMB important when doing a complete fit to all data

Neutrino-mass limits Many authors using different inputs and different priors Fogli et al hep-ph/0608060 Absolute mass scale

N_effective of neutrinos (radiation) Neff limited by CMB+LSS+… Change in expansion history Radiation smoothes small scale structure Hannestad astro-ph/0510582 CNB “detected” Generalization to thermal relics Hannestad & Raffelt astro-ph/0312154

Caveats Most bounds in standard minimal in fact M=Mixed Care with degeneracies degeneracy m_nu and w broken by BAO Hannestad astro-ph/0505551 Minimal standard model (standard neutrinos) Experimental systematics (Remember 4 He) Bias luminous/dark Bias-free limit Kristiansen et al astro-ph/0611761

Future Lesgourgues, Pastor hep-astro/0603494

Early universe, Late universe Neutrinos in the very early universe Sakharov conditions Problems of GUTS for baryogenesis Leptogenesis can generate B-asymmetry Decays of heavy Majoranas of see-saw. Relation to nu mass and mixing phases Neutrinos in the very late universe Scale of Dark Energy might be nu mass - Mass Varying Neutrinos - nu condensate

Conclusion plays an active role in cosmology properties constrained by cosmology (complementary to other type of constraints)